Question: Simplify the following expression: $ y = \dfrac{-2t - 3}{9} - \dfrac{1}{5} $
Explanation: In order to subtract expressions, they must have a common denominator. Multiply the first expression by $\dfrac{5}{5}$ $ \dfrac{-2t - 3}{9} \times \dfrac{5}{5} = \dfrac{-10t - 15}{45} $ Multiply the second expression by $\dfrac{9}{9}$ $ \dfrac{1}{5} \times \dfrac{9}{9} = \dfrac{9}{45} $ Therefore $ y = \dfrac{-10t - 15}{45} - \dfrac{9}{45} $ Now the expressions have the same denominator we can simply subtract the numerators: $y = \dfrac{-10t - 15 - 9 }{45} $ Distribute the negative sign: $y = \dfrac{-10t - 15 - 9}{45}$ $y = \dfrac{-10t - 24}{45}$